Adds basic emoji index and search by name/unicode.

* Adds index.json from phantom_open_emoji as basic set meta-data
* Adds Emoji::Index class that returns emoji as a hash of string attributes
* Add index lookups by name and 'moji' unicode character
Fix rake test test_files inclusion.
Adds Emoji lookup APIs and config

* Emoji.image_url_for_name
* Emoji.image_url_for_unicode_moji
* Config via asset_host/asset_path params for URL generation
Adds basic rvmrc
API for replacing Unicode moji w/ emoji img tags

* `Index.unicode_moji_regex` matches all known moji
* `Emoji.replace_unicode_moji_with_images` escapes any markup in string and then replaces unicode moji with img tags pointing to proper moji image_url
Add emoji class to generated img
Fix default asset_host and url protocol handling.
Don't escape/process strings w/out an emoji.

Ensure the string has at least one emoji character to be replaced before escaping/`gsub`ing anything.  Just return original string.
Remove original image assets.
Adds 64x64 emoji image assets.
Merge branch 'feature/64x64_imgs' into polar
Remove retina image asset feature.
Handle html_safe input/output with escaping.

* Escape strings not marked html_safe?
* Mark outgoing strings html_safe
Merge branch 'feature/image_replacement' into polar
Add tests for html_safe handling/escaping

* Introduces mocha as a dev dependency
* Verify `html_safe?` checking/escaping
* Verify output marked `html_safe`
Merge branch 'feature/image_replacement' into polar
replace_unicode_moji_with_images handles nil

Return the input string unless it's non-nil and contains one or more emoji.
Update README.md

* Usage examples and config
* Bundle/test callouts
Merge branch 'feature/image_replacement'
Merge remote-tracking branch 'origin/feature/64x64_imgs'